Cu-doped SnO₂/rGO nanocomposites for ultrasensitive H₂S detection at low temperature

Hydrogen sulfide (H₂S) detection remains a significant concern and the sensitivity, selectivity, and detection limit must be balanced at low temperatures. Herein, we utilized a facile solvothermal method to prepare Cu-doped SnO₂/rGO nanocomposites that have emerged as promising candidate materials for H₂S sensors. Characterization of the Cu-SnO₂/rGO was carried out to determine its surface morphology, chemical composition, and crystal defects. The optimal sensor response for 10 ppm H₂S was ~1415.7 at 120 °C, which was over 320 times higher than that seen for pristine SnO₂ CQDs (R_a/R_g = 4.4) at 280 °C. Moreover, the sensor material exhibited excellent selectivity, a superior linear working range (R² = 0.991, 1-150 ppm), a fast response time (31 s to 2 ppm), and ppb-level H₂S detection (R_a/R_g = 1.26 to 50 ppb) at 120 °C. In addition, the sensor maintained a high performance even at extremely high humidity (90%) and showed outstanding long-term stability. These superb H₂S sensing properties were attributed to catalytic sensitization by the Cu dopant and a synergistic effect of the Cu-SnO₂ and rGO, which offered abundant active sites for O₂ and H₂S absorption and accelerated the transfer of electrons/holes.